The widespread use of modern steel harrows in the United States was delayed until the 1880s, roughly fifty years after the massive shift to cast iron and steel plows. When tractors were introduced, they began to be used universally for primary tillage, while animals continued to be used for other types of soil preparation.
As for government intervention, the historical record is quite clear. Mechanization in today's industrial countries did not depend on direct government involvement in machinery development, production, technology choice, or finance.10 The same is true of the most successful experiences in the developing world, such as the mechanization of milling, pumping, or harvest processing. Once economic conditions have produced effective demand for machinery, private firms have responded rapidly in the developed world.